Cooling apparatus

ABSTRACT

A heat sink comprises a core member comprising at least one core member first surface. The core member first surface is adapted to contact or be located adjacent at least a portion of the heat source. At least one outer peripheral surface is located on the core member. At least one cooling fin is operatively connected to the outer peripheral surface and extends in a direction substantially normal to the core member first surface. At least a portion of the outer peripheral surface is tapered, wherein the circumference of the outer peripheral surface in the proximity of the first surface is greater than the circumference of the outer peripheral surface not in the proximity of the first surface.

This application is a continuation-in-part of U.S. application Ser. No.10/006412 of Wagner filed on Dec. 3, 2001, now U.S. Pat. No. 6,561,261,which is hereby incorporated by reference for all that is disclosedtherein.

FIELD OF THE INVENTION

The present invention relates generally to cooling devices.

BACKGROUND OF THE INVENTION

Electronic components, such as integrated circuits, are increasinglybeing used in different devices. One prevalent example of a device usingintegrated circuits is the computer. The central processing unit orunits of most computers, including personal computers, is typicallyconstructed from a plurality of integrated circuits. Integrated circuitsare also used in other computer circuitry. For example, interface andmemory circuits typically comprise several integrated circuits.

During normal operation, many electronic components, such as integratedcircuits, generate significant amounts of heat. If this heat is notcontinuously removed, the electronic component may overheat, resultingin damage to the component and/or a reduction in its operatingperformance. For example, an electronic component may encounter thermalrunaway, which may damage the electronic component. In order to avoidsuch problems caused by overheating, cooling devices are often used inconjunction with electronic components.

One such cooling device used in conjunction with electronic componentsis a heat sink. A heat sink is a device that draws heat from anelectronic component and convects the heat to the surroundingatmosphere. The heat sink is usually placed on top of, and in physicalcontact with, the heat generating electronic component so as to providethermal conductivity between the electronic component and the heat sink.

One method of increasing the cooling capacity of heat sinks is byincluding a plurality of cooling fins attached to the heat sink and acooling fan that forces air past the cooling fins. The cooling finsserve to increase the surface area of the heat sink and, thus, increasethe convection of heat from the heat sink to the surrounding atmosphere.The fan serves to force air past the fins, which further increases theconvection of heat from the heat sink to the surrounding atmosphere.This increased convection, in turn, allows the heat sink to draw moreheat from the electronic component. In this manner, the heat sink isable to draw a significant amount of heat away from the electroniccomponent, which serves to further cool the electronic component.

Cooling fins with larger surface areas, however, tend to havesignificant barrier layers of air on the cooling fin surfaces when airis forced past the cooling fins. An air barrier layer is air that isadjacent the surface of a cooling fin and remains substantiallystationary relative to the cooling fin as air is forced past the coolingfin. Thus, a significant barrier layer may result in the air beingforced past cooling fins not being able to effectively remove heat fromthe cooling fins. Accordingly, increasing the area of individual coolingfins may not result in a proportional cooling capability of the heatsink.

Another problem associated with large cooling fins is that they occupylarge spaces within an electronic device, which could otherwise be usedto reduce the size of the electronic device. Large cooling fins alsooccupy space that could otherwise be used to increase the concentrationof electronic components located within the electronic device.Electronic devices are becoming much smaller, thus, a reduced space or ahigher concentration of electronic components within the electronicdevices is beneficial. The use of large cooling fins tends to increasethe size of the electronic devices or reduce the concentration ofelectronic components located therein.

Therefore, a device and/or method is needed to overcome some or all theaforementioned problems.

SUMMARY OF THE INVENTION

The present invention is directed toward a heat sink for removing heatfrom a heat source. The heat sink may comprise a core member comprisingat least one core member first surface. The core member first surface isadapted to contact or be located adjacent at least a portion of the heatsource. At least one outer peripheral surface is located on the coremember. At least one cooling fin is operatively connected to the outerperipheral surface and extends in a direction substantially normal tothe core member first surface. At least a portion of the outerperipheral surface is tapered, wherein the circumference of the outerperipheral surface in the proximity of the first surface is greater thanthe circumference of the outer peripheral surface not in the proximityof the first surface.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a top perspective view of a cooling device having a pluralityof fin rings and a fan.

FIG. 2 is a top perspective view of the cooling device of FIG. 1 havinga single first fin ring and without the fan.

FIG. 3 is a top perspective view of the core member of the coolingdevice of FIG. 1.

FIG. 4 is a side view of the core member of the cooling device of FIG. 1without any fin rings associated therewith.

FIG. 5 is a cut away, schematic illustration of the cooling device ofFIG. 1.

FIG. 6 is a side view of the cooling device of FIG. 1 located adjacent aheat generating electronic device.

FIG. 7 is a top perspective view of a fin ring of the type illustratedin the cooling device of FIG. 2.

FIG. 8 is a top perspective view of the cooling device of FIG. 2 havinga second fin ring located adjacent the first fin ring.

FIG. 9 is a side view of the cooling device of FIG. 6 with a shroudattached thereto.

FIG. 10 is a top perspective view of the cooling device of FIG. 2 withthe addition of a compression ring.

FIG. 11 is a side view of the cooling device of FIG. 1 with a pluralityof compression rings attached thereto.

FIG. 12 is a top cutaway view of a cooling device having a ribbon-typecooling fin associated therewith.

FIG. 13 is the cooling device of FIG. 12 with the addition of a shroudencompassing the core and ribbon-type cooling fin.

FIG. 14 is a side, schematic illustration of a cooling device havingcooling fins extending parallel to the core.

FIG. 15 is a side view of an embodiment of the core member of FIG. 3being constructed from two components.

FIG. 16 is a side view of a cooling device having a reduced shroud.

DETAILED DESCRIPTION

A non-limiting embodiment of a cooling device 100 is shown in FIG. 1.The cooling device 100 may have an air blowing device 110 associatedwith a heat sink 200. In the non-limiting embodiment described herein,the air blowing device 110 is a fan and is sometimes referred to as thefan 110. However, it is to be understood that the air blowing device 110may be other devices, such as duct work that causes air to be blown ontothe heat sink 200. The following description describes the heat sink 200followed by a description of the fan 110. A description of the operationof the fan 110 associated with the heat sink 200 follows theirindividual descriptions.

Referring to FIG. 2, which shows a partially constructed heat sink 200,the heat sink 200 may have a core member 210 (sometimes referred toherein simply as the core 210) with a first fin ring 281 locatedadjacent the core 210. For illustration purposes, FIG. 2 shows only asingle first fin ring 281 attached to or otherwise operativelyassociated with the core 210. Further below in this description, theheat sink 200 will be described having a plurality of fin rings 240,FIG. 1, operatively associated with the core 210. The first fin ring 281and other fin rings described herein are sometimes referred to ascooling fin devices.

A top perspective view of the core 210 is shown in FIG. 3. The view ofFIG. 3 is similar to the core 210 of FIG. 2 without any fin ringsattached thereto. The core 210 may be made of a thermally conductivematerial, such as copper or aluminum. The core 210 may have a topsurface or portion 214 and a lower surface or portion 216. A height H1may extend between the top portion 214 and the lower portion 216 andmay, as an example, be approximately 3.0 centimeters. The top portion214 may be substantially round and may have a diameter D1 associatedtherewith. The diameter D1 may, as an example, be approximately 3.0centimeters. The diameter D1 and height H1, however, are dependent onthe specific cooling application of the cooling device 100 and may varyaccordingly both in size and shape.

The core 210 may have an outer peripheral surface 212 (sometimes simplyreferred to herein as the peripheral surface 212) located between thetop portion 214 and the lower portion 216. The peripheral surface 212 ofthe core 210 has a cylindrical portion 217 and a tapered portion 218. Itshould be noted that the use of a partially cylindrical core and, thus,a cylindrical portion 217 is for illustration purposes only. The core210 may be virtually any shape that serves to allow the fin rings to beassociated therewith. For example, the core 210 and, thus, the topportion 214, may be oval. It should also be noted that the core 210shown in FIG. 3 has a single peripheral surface 212. Other embodimentsof the core 210 may have several peripheral surfaces. For example, theperipheral surface 212 may be divided into several portions or may formseveral surfaces.

The cylindrical portion 217 of the core 210 has a height H2 and thetapered portion 218 has a height H3. As shown in FIG. 3, the cylindricalportion 217 of the core 210 extends between the top portion 214 and aportion of the peripheral surface 212 indicated by a dashed line. Thetapered portion 218 extends between the dashed line and the lowerportion 216. In the embodiment described herein, the fin rings shown inFIG. 2 are attached to the cylindrical portion 217 of the core 210. Asdescribed in greater detail below, the tapered portion 218 serves todivert air from the core 210, which increases the efficiency of the heatsink 100, FIG. 1.

Referring to FIG. 4, which is a side view of the core 210 of FIG. 3, thelower portion 216 of the core 210 is adapted to be in thermal contact orphysical contact with a heat generating device 330. In the embodimentdescribed herein, the lower portion 216 of the core 210 is adapted tocontact a top surface 332 of the heat generating device 330. The contactbetween the core 210 and the heat generating device 330 provides for thetransfer of heat from the heat generating device 330 to the core 210.For example, in the situation where the heat generating device 330 is anintegrated circuit, the top surface 332 of the integrated circuit istypically a planar surface. Accordingly, the lower portion 216 of thecore 210 may be a substantially planar surface and may have an area thatis approximately the same as or greater than the area of the top surface332 of the heat generating device 330.

As shown in FIG. 3 and FIG. 4, the circumference or perimeter of theperipheral surface 212 of the core 210 is the greatest in the proximityof the lower portion 216 of the core 210. More specifically, thecircumference of the peripheral surface 212 increases in the taperedportion 218 of the core 210 toward the lower portion 216 of the core210. Accordingly, the circumference is at a minimum in the proximity ofthe cylindrical portion 217 of the core and is at a maximum in theproximity of the lower portion 216. This tapering of the core 210 causesairflow generated by the air blowing device 110 to be freely exhaustedaway from the lower portion 216 of the core 210 as shown in FIG. 4. Asthe airflow transitions from a direction toward the heat generatingdevice 330 to a direction away from the heat generating device 330, backpressure and/or turbulence are reduced by the tapered portion 218.Therefore, a greater amount of air may pass adjacent the core 210 andmay remove a greater amount of heat from the core 210. With anadditional and brief reference to FIG. 1, the tapering of the core 210enables a greater amount of air to pass the cooling fins, which in turnincreases the cooling capability of the heat sink 200.

The airflow shown in FIG. 4 is parallel to the peripheral surface 212.More specifically, the airflow is shown commencing at the air blowingdevice 110 and extending in a substantially straight line to the taperedportion 218, where it is then terminated by being exhausted from theheat sink 200. Such an airflow may exist in a situation where theairflow generated by the air blowing device 110 extends substantiallynormal to the air blowing device 110. For example, this airflow mayexist in a situation where the air blowing device 110 is a duct thatdelivers forced air from a remote location.

Referring briefly to FIG. 5, an embodiment of the cooling device 100 mayhave an airflow that spirals the core 210. For example, in a situationwhere the air blowing device 110 is a fan, the airflow may substantiallyspiral around the core 210 as is described in greater detail below. Withadditional reference to FIG. 1, the spiraling airflow shown in FIG. 5improves the airflow associated with the fin rings as is described ingreater detail below.

Referring again to FIG. 4, in the embodiment of the core 210 illustratedherein, the peripheral surface 212, including the cylindrical portion217 and the tapered portion 218, are continuous, meaning that there areno discontinuities in the peripheral surface 212. The continuoussurfaces enable the airflow shown in FIG. 4 to be less susceptible toturbulence and enables greater airflow. In another embodiment of thecore 210, the peripheral surface 212 has discontinuities (not shown)and, thus, only portions of the peripheral surface 212 contact the finrings, FIG. 2.

Having described the core 210, FIG. 2, the first fin ring 281, FIG. 7,will now be described in greater detail. FIG. 7 is a top perspectiveview of the first fin ring 281 separated from the core 210, FIG. 2, andis representative of the remaining fin rings 240 that may be associatedwith the core 210 as illustrated in FIG. 6. The first fin ring 281 mayhave a collar 244 with a plurality of cooling fins 246 attached theretoor otherwise associated therewith. The collar 244 may have an innerperipheral surface 248 having an upper ring portion or side 270 and alower ring portion or side 272. The upper portion 270 and the lowerportion 272 may be separated by a height H3, which may, as an example,be approximately 0.25 centimeters. The upper ring portion 270 and thelower ring portion 272 may be located on substantially parallel planes.A reference axis BB may pass through the center point 274 of a circledefined by the collar 244. The reference axis BB may be substantiallynormal to the planes defined by the upper ring portion 270 and the lowerring portion 272.

The inner peripheral surface 248 has a perimeter associated with it,which in the embodiment described herein is a cylindrical surfaceextending between the upper portion 270 and the lower portion 272. Theperimeter of the inner peripheral surface 248 may be substantiallysimilar to the perimeter of the cylindrical portion of the peripheralsurface 212, FIG. 2, of the core 210. For example, the inner peripheralsurface 248 may be round and may have a diameter D2 that isapproximately the same or slightly smaller than the diameter D1 of thecore 210, FIG. 2. In one embodiment of the heat sink 200, FIG. 2, thediameter D1 of the core 210 and the diameter D2, FIG. 7, of the firstfin ring 281 are appropriately sized so as to cause an interference fitbetween the first fin ring 281 and the core 210 as is described ingreater detail below.

The collar 244 may have an outer surface 252 wherein the cooling fins246 are attached to the outer surface 252. Reference is made to a firstfin 250, which is representative of all the cooling fins 246 and theirassociation with the outer surface 252. The first fin 250 may have amounting portion 256, an end portion 258, a surface 260, an upper end262, and a lower end 264. The surface 260 may be defined by theboundaries of the mounting portion 256, the end portion 258, the upperend 262, and the lower end 264. The surface 260 may be substantiallyplanar. A length D3 may extend between the mounting portion 256 and theend portion 258. The length D3 may, as an example, be approximately 11to 13 millimeters. A length D4 may extend between the upper end 262 andthe lower end 264. In one embodiment the length D4 is relatively smallin order to reduce the boundary layer of air that may accumulate on thesurface 260 of the first fin 250 when air is forced past the surface260. The length D4 may, as an example, be approximately 3.25millimeters. The mounting portion 256 may be a twisted portion of thefirst fin 250 and may serve to create an angle Φ between the end portion258 and the reference axis BB. The angle Φ may, as an example, beapproximately 45 degrees. It should be noted that the angle Φ may bedetermined by the direction of the airflow as shown in FIG. 4 and FIG. 5and as described in greater detail below.

The collar 244 and the cooling fins 246 may be made of a heat conductingmaterial such as aluminum or copper. The junction between the collar 244and the mounting portion 256 of the cooling fins 246 may conduct heatwith minimal thermal resistance. For example, the collar 244 may beintegrally formed with the cooling fins 246 or they may be weldedtogether. In a non-limiting example of manufacturing the first fin ring281, the first fin ring 281 may be fabricated from a single metal sheet,such as a copper or aluminum sheet. The metal sheet may, as an example,have a thickness of approximately 15 to 20 thousandths of an inch.Fabrication of the first fin ring 281 may commence with stamping thecollar 244 out of the metal sheet. The collar 244 is essentially acircular cutout having a diameter D2 and a height H2. Accordingly, thestamping process forms the diameter D2 and the height H2 of the collar244. The cooling fins 246 may then be stamped out of the metal sheet.For example, the cooling fins 246 may be cut out of the metal sheet viaa conventional stamping process. The metal sheet may then be placed intoa dye that twists the cooling fins 246 at the mounting portion 256 inorder to form the angle Φ.

Referring again to FIG. 2 and FIG. 4, the first fin ring 281 may bepressed onto the core 210 in a conventional manner to form aninterference fit between the first fin ring 281 and the core 210. Theinterference fit is a result of a cylindrical portion 217 of the surface212 of the core 210 being substantially the same as the perimeter of theinner peripheral surface 248, FIG. 7, of the first fin ring 281.Accordingly, the diameter D1 of the core 210 is substantially the sameor slightly larger than the diameter D2, FIG. 7, of the first fin ring281. As shown in FIG. 2, the first fin ring 281 may be located in thevicinity of the junction of the cylindrical portion 217 and the taperedportion 218 of the core 210. Referring to FIG. 8, which is the heat sink200 of FIG. 2 with an additional fin ring attached thereto, after thefirst fin ring 281 has been pressed onto the core 210 a second fin ring282 may be pressed onto the core 210. The process of pressing fin rings240 onto the core 210 may continue until the surface 212 of the core 210is substantially covered with fin rings 240 as illustrated in FIG. 6.

FIG. 6 illustrates nine fin rings 240 affixed to the core 210. The finrings 240 are referred to individually as the first through the ninthfin rings and referenced numerically as 281 through 289 respectively.The plurality of fin rings 240 substantially increases the surface areaavailable on the heat sink 200 for convecting heat to the surroundingatmosphere. In addition, the fin rings 240 are relatively thin, whichincreases their ability to convect heat to the surrounding atmosphere byminimizing the air resistance through the fin rings 240 as is describedbelow. As illustrated in FIG. 6, the cooling fins 246 are substantiallyplanar and are located on planes that are substantially parallel to eachother. As described in greater detail below, the planar arrangement ofthe cooling fins 246 forms channels that serve to guide air past thecooling fins 246, which increases convection of heat to the surroundingatmosphere. The planar arrangement of the fin rings 240 is describedbelow with reference to the schematic illustration of FIG. 5.

In the embodiment of the heat sink 200 described herein, the fin rings240 are arranged so that the cooling fins 246 are nested, meaning thatthey bisect airflow patterns. This nesting is illustrated in FIG. 5between the seventh fin ring 287, the eighth fin ring 288, and the ninthfin ring 289. The cooling fins 246 of the seventh fin ring 287 and theninth fin ring 289 are located on the same plane and thus form an airchannel therebetween. This air channel is bisected by the cooling fins246 of the eighth fin ring 288. This bisection causes some turbulence inthe airflow within the cooling fins 246, which serves to break up orreduce the air barrier layer. Thus, the cooling capability of the heatsink 200 is improved. It should be noted that the nesting of the finrings 240 enables a great number of cooling fins 246 to be associatedwith the heat sink 200.

Having described the heat sink 200, the fan 110 and other air blowingdevices will now be described followed by a description of theassociation between the heat sink 200 and the fan 110.

Referring again to FIG. 6, the fan 110 may be a conventional electricfan. In other embodiments described below, the fan 110 is replaced withan air blowing device, such as duct work. The fan 110 may, as anexample, be of the type commercially available from the MatsushitaElectric Corporation as Model FBA06T12H and sold under the tradenamePANAFLO. The fan 110 may have a rotating portion 112, wherein therotating portion 112 may have a top portion 114, a lower portion, notshown in FIG. 6, and a peripheral side wall 116. A reference axis AA mayextend through the center of the top portion 114 and may besubstantially normal to the top portion 114. As described in greaterdetail below, the reference axis AA may define a center of rotation ofthe rotating portion 112. A direction 130 is used herein to describe therotational direction of the rotating portion 112 about the referenceaxis AA.

The peripheral side wall 116 of the fan 110 may have a plurality ofcirculating fins 118 attached thereto. The circulating fins 118 may besubstantially identical to each other. A first circulating fin 119 and asecond circulating fin 120 are used as a reference to describe all thecirculating fins 118. The circulating fins 119, 120 may have an innerside 121, an outer side 122, an upper side 124, and a lower side 126.The sides may define the boundaries of a surface 128. The inner side 121may be attached to the peripheral side wall 116 of the rotating portion112 in a conventional manner. For example, the circulating fins 119, 120may be adhered to or integrally formed with the side wall 116. Theattachment of the circulating fins 119, 120 to the side wall 116 maydefine an angle e between the surface 128 and the reference axis M. Theangle θ may, as an example, be about 45 degrees. In one embodiment, theangle θ is equal to 90 degrees minus the angle Φ of FIG. 7. As describedin greater detail below, the angle θ may serve to determine thedirection of air flow generated by the fan 110 as the rotating portion112 rotates in the direction 130.

Having described the fan 110 and the heat sink 200 separately, theirassociation with each other will now be described.

As illustrated in FIG. 6, the fan 110 may be located adjacent the topportion 214, FIG. 2, of the core 210. The fan 110 may, as examples, beattached to the core 210 by the use of fasteners, e.g., screws, or itmay be adhered to the core 210. It should be noted, however, that thefan 110 does not need to be physically attached to the core 210 and thatthe fan 110 only needs to be able to force air past the cooling fins246.

FIG. 5, illustrates the air flow between the fan 110 and the heat sink200 in one embodiment of the cooling device 100. It should be noted thatfor illustration purposes the heat sink 200 illustrated in FIG. 5 onlyshows a limited number of fin rings 240 and cooling fins 246. Asdescribed above, the first circulating fin 119 is positioned at an angleθ relative to the reference axis AA. In one embodiment, the angle θ isapproximately forty-five degrees. The cooling fins 246 are positioned atan angle Φ relative to the reference axis AA, which, in the embodimentdescribed herein, is approximately 45 degrees. A reference axis CC mayextend parallel to the end portions 258 of the cooling fins 246 and maybe substantially perpendicular to the surface 128 of the firstcirculating fin 119. An air flow direction 290 commences at the surface128 of the first circulating fin 119 and extends parallel to thereference axis CC, which, in this embodiment, is normal to the surface128. The air flow direction 290 is the direction that air flows as thefirst circulating fin 119 rotates in the direction 130.

When the rotating portion 112 rotates in the direction 130, the firstcirculating fin 119 forces air to circulate past the cooling fins 246.The airflow generated by the rotating first circulating fin 119 flows inthe air flow direction 290, which is parallel to the reference axis CC.The air flow direction 290 is, accordingly, parallel to the end portions258 and the surfaces 260 of the cooling fins 246. This relation betweenthe air flow direction 290 and the cooling fins 246 allows air generatedby the rotating first circulating fin 119 to pass over the surfaces 260of the cooling fins 246 with little resistance. In addition, this airflow direction 290 relative to the cooling fins 246 reduces any eddycurrents that may, in turn, reduce the air flow through the heat sink200. In addition, as described above, the cooling fins 246 are thinenough to minimize air resistance, but thick enough to transfer heatfrom the core 210. Thus, the cooling fins 246 cause little resistance tothe air flow through the heat sink 200, which in turn, allows for themaximum convection of heat from the cooling fins 246 to the surroundingatmosphere. As described above, the cooling fins 246 may be small enoughto minimize the air barrier layer present on their surfaces, which inturn increases the cooling capability of the cooling device 100.

The thin cooling fins 246 and their placement relative to each otherallow them to be condensed or “nested” which in turn allows a greaternumber of cooling fins 246 to convect heat to the surroundingatmosphere. In addition, the placement of the fin rings 240 and thecooling fins 246 create channels for air to flows past the cooling fins246. One such channel is defined by the reference axis CC, which isparallel to the air flow direction 290. Other channels are parallel tothe channel defined by the reference axis CC and other channels bisectthe channel defined by the reference axis CC.

Referring again to FIG. 6, having described the cooling device 100, itwill now be described cooling a heat generating device 330 that ismounted to a top surface 342 of a printed circuit board 340. The heatgenerating device 330 is described herein as being an integrated circuitthat generates heat when it is in use. The heat generating device 330may have a top surface 332 wherein most of the heat generated by theheat generating device 330 flows from the top surface 332 in a direction334. The cooling device 100 may be operatively associated with the heatgenerating device 330 so that the lower portion 216 of the core 210 isin thermal contact with the top surface 332 of the heat generatingdevice 330. In order to assure thermal conductivity between the heatgenerating device 330 and the cooling device 100, the cooling device 100may be attached to the printed circuit board 340 in a conventionalmanner so as to bias the cooling device 100 onto the heat generatingdevice 330.

When the heat generating device 330 is in use, it generates more heatthan it can dissipate alone. Heat accumulates in the top surface 332 ofthe heat generating device 330 and generally flows in the direction 334.The heat generated by the heat generating device 330 is absorbed intothe core 210 by virtue of the thermal contact between the top surface332 of the heat generating device 330 and the lower portion 216 of thecore 210. Thus, the temperature of the heat generating device 330 isreduced by the absorption of heat into the core 210. The heat absorbedby the core 210 dissipates to the surface 212 where some of the heat isconvected directly to the surrounding atmosphere. The interference fitsbetween the fin rings 240 and the core 210 cause the majority of theheat dissipated to the surface 212 of the core 210 to transfer to thefin rings 240 and into the cooling fins 246.

Simultaneous to heat being absorbed into the core 210 and dissipated tothe cooling fins 246, the fan 110 forces air to flow in the air flowdirection 290 past the surfaces 260 of the cooling fins 246. Morespecifically, the fan 110 may draw air into the cooling device 100 alongan air flow direction 360. The air passes through the heat sink 200 inthe air flow direction 290 and is exhausted along an air flow direction362. Accordingly, the heat in the cooling fins 246 is convected into thesurrounding atmosphere. As described above, the tapered portion 218 ofthe core 210 enables the air to flow freely from the heat sink 200,which in turn increases the amount of air that can be forced through theheat sink 200.

The rate of heat transfer between the core 210 and the cooling fins 246is proportional to the temperature difference between the cooling fins246 and the surface 212 of the core 210. Likewise, the heat transferfrom the heat generating device 330 to the core 210 is proportional tothe temperature of the core 210. Accordingly, a higher rate of heattransfer from the heat generating device 330 can be accomplished bysignificantly cooling the cooling fins 246. The temperature of thecooling fins 246 is proportional to their position relative to the heatgenerating device 330, wherein the cooling fins 246 positioned close tothe heat generating device 330 are hotter than those positioned furtherfrom the heat generating device 330. By forcing relatively cool air inthe air flow direction 290, all the cooling fins 246 are exposed torelatively cool air, which reduces their temperature. The relativelycool cooling fins 246 are, thus, able to transfer heat from the surface212 of the core 210 at a high rate, which in turn, cools the core 210 ata high rate. The cooler core 210 is then able to remove a great amountof heat at a high rate from the heat generating device 330.

Due to inherent air restrictions in the heat sink 200 caused by thecooling fins 246, not all the air forced into the heat sink 200 by thefan 110 passes by the cooling fins 246. For example, the fan 110 maycause air pressure to build up in the cooling fins 246, which in turn,causes some air to leave the heat sink 200 without passing by all thefin rings 240. The heat sink 200 of FIG. 6 shows that some air mayfollow an air flow direction 370 and may be exhausted from the heat sink200 without passing by all of the cooling fins 246. Accordingly, the airfollowing the air flow direction 370 may not be used efficiently.

Referring to FIG. 9, in order to assure all the air drawn into thecooling device 100 passes the cooling fins 246, a shroud 350 may beadded to the cooling device 100. The shroud 350 may, as an example, be aduct that fits over the heat sink 200 and does not allow air to escapefrom the heat sink 200 until it has passed by all the cooling fins 246.Thus, all the air entering the cooling device 100 along the air flowdirection 360 is exhausted from the cooling device 100 along the airflow direction 362.

The shroud 350 may have an upper portion 352 and a lower portion 354.The upper portion 352 may substantially encompass the fan, not shown inFIG. 9, and the lower portion 354 may substantially encompass the heatsink 200. A plurality of openings 356 may be formed into the upperportion 352 in order to facilitate air flow through the cooling device100. More specifically, air may flow in an air flow direction 364through the openings 356 where it joins the air flowing along the airflow direction 360. Accordingly, the openings 356 may serve to increasethe volume of air that passes the cooling fins 246, which in turnincreases the convection of heat to the surrounding atmosphere. Theshroud 350 is illustrated as having slot-shaped openings 364 that areslanted to correlate with the angle of the first circulating fin 119,FIG. 6. The openings 364 described herein are positioned at the angle θrelative to the reference axis AA, which in the embodiment describedherein is forty-five degrees.

Having described an embodiment of the cooling device 100, otherembodiments of the cooling device 100 will now be described.

Referring again to FIG. 5, the cooling device 100 has been describedhere as having the fin rings 240 pressed onto the core 210. Pressing thefin rings 240 onto the core 210 creates interference fits between thefin rings 240 and the core 210, which provide for high thermalconductivity between the core 210 and the fin rings 240. Theinterference fits, however, require that the core 210 and the fin rings240 be manufactured to precise specifications. If precise manufacturingspecifications are not achieved, the fin rings 240 may be loose on thecore 210 or the fin rings 240 may not be able to be pressed onto thecore 210.

Referring to FIG. 10, the above-described problems of controlling thespecifications of the fin rings 240, FIG. 6, may be overcome by theaddition of compression rings partially encompassing the core 210. Inthis embodiment of the heat sink 200, interference fits between the finrings 240 and the core 210 are not required. A compression ring 380 mayabut the top side of the first fin ring 281. A second compression ring,not shown, may abut the bottom side of the first fin ring 281. Thecompression ring 380 may be a ring of thermally conductive material,such as copper or aluminum, that is pressed onto the core 210 and firmlyabuts the first fin ring 281. Heat in the core 210 may then betransferred to the first fin ring 281 via the compression ring 380.Accordingly, the use of the compression ring 380 permits the first finring 281 to be manufactured to looser specifications than thosedescribed above. In one embodiment, the compression rings forminterference fits with the fin rings and the core when they are pressedtogether. For example, the compression rings may distort to form theinterference fits.

A plurality of compression rings may be pressed or otherwise placed ontothe core 210 during the manufacturing process of the heat sink 200. Forexample, one compression ring, not shown in FIG. 10, may be pressed ontothe core 210 in the vicinity of the lower portion 216. The first finring 281 may then be placed over the core 210 so as to abut thecompression ring located in the vicinity of the lower portion 216. Thecompression ring 380 may then be pressed onto the core 210 so as to abutthe first fin ring 281. Accordingly, the first fin ring 281 issandwiched between compression rings. The compression rings may then beforced together to so that the first fin ring 281 is tightly compressedbetween them. This compression serves to enhance the thermalconductivity between the compression rings and the first fin ring 281,which in turn enhances the cooling capability of the heat sink 200.

Referring to FIG. 11, a plurality of compression rings may be pressedonto the core 210. The heat sink 200 illustrated in FIG. 11 is similarto the heat sink 200 illustrated in FIG. 6, however, the heat sink 200of FIG. 11 has a plurality of compression rings placed or otherwisepressed onto the core 210. The heat sink 200 may have a top compressionring 390 located in the vicinity of the top portion 214 of the core 210.The heat sink 200 may also have a bottom compression ring 392 located inthe vicinity of the junction of the cylindrical portion 217 and thetapered portion 218 of the core 210. A plurality of inner compressionrings 394 may be pressed onto the core 210, wherein one of the pluralityof inner compression rings 394 is located between each of the fin rings240.

The heat sink 200 of FIG. 11 may be manufactured by first pressing thebottom compression ring 392 onto the core 210. The first fin ring 281may then be slipped over the core 210 and placed near the bottomcompression ring 392. An inner compression ring 394 may then be pressedonto the core so as to sandwich the first fin ring 281 betweencompression rings. The second fin ring 282 may then be slipped over thecore 210 to abut the previously pressed on inner compression ring 394.The process of alternating fin rings 240 and inner compression rings 394continues until all of the fin rings 240 have been placed onto the core210. Accordingly, an inner compression ring 394 is located between eachfin ring 240. The top compression ring 390 may then be pressed onto thecore 210. In order to assure that thermal contact exists between the finrings 240 and the compression rings 390, 392, 394, the top compressionring 390 and the bottom compression ring 392 may be pressed together.This will cause the fin rings 240 to contact all the compression rings390, 392, 394, which increases the thermal conductivity between thesurface 212 of the core 210 and the fin rings 240.

Referring again to FIG. 6, in one embodiment of the cooling device 100,the core 210 may be a heat pipe or have a heat pipe located therein. Aheat pipe is a device that is known in the art and serves to rapidlytransfer heat. Thus, the interior of the core 210 may be a partiallyevacuated chamber containing a small amount of a liquid. When the core210 is cool, the liquid is located in the vicinity of the lower portion216 of the core 210. The liquid evaporates when it is heated by the heatgenerating device 330. The vapor from the evaporated liquid condenses onthe sides of the core 210 and, thus, transfers its heat to the sides ofthe core 210. The heat may then quickly transfer to the surface 212 ofthe core 210. The heat may then be convected to the surroundingatmosphere as described above. The use of the heat pipe substantiallyincreases the heat transfer through the core 210, which in turnincreases the cooling capability of the cooling device 100. Examples ofheat pipes are disclosed in the following United States patents andpatent applications, which are all hereby incorporated by reference forall that is disclosed therein: Ser. No. 09/376,627 of Wagner et al. forCOOLING APPARATUS FOR ELECTRONIC DEVICES; registration number U.S. Pat.No. 5,694,295 of Masataka et al. for HEAT PIPE AND PROCESS FORMANUFACTURING THE SAME.

The heat sink 200 has been described herein as having a plurality ofcooling fins 246 that extend radially from the core 210. Otherembodiments of the heat sink 200 have different cooling finconfigurations as described in greater detail below.

One embodiment of a fin configuration is illustrated in FIG. 12 and usesa ribbon-type cooling fin, which is sometimes referred to herein as acooling ribbon 400. The cooling ribbon 400 may, as an example, beconstructed from a single piece of a thermally conductive material, suchas a sheet of copper or aluminum. Alternatively, the cooling ribbon 400may be extruded in a conventional manner. The cooling ribbon 400 mayhave a plurality of contact portions 410 and end portions 412. Thecontact portions 410 may serve to contact the surface 212 of the core210 and may, thus, be points where heat is transferred from the core 210into the cooling ribbon 400. The end portions 412 may be portions of thecooling ribbon 400 that are located furthest from the surface 212 of thecore 210. A plurality of inner air channels 420 may be located betweenthe surface 212 of the core 210 and the end portions 412. A plurality ofouter air channels 422 may be located between the contact portions 410and the cooling ribbon 400.

The cooling ribbon 400 may be pressed onto the core 210. For example, inone embodiment of the heat sink 200, a single cooling ribbon 400 ispressed onto the core 210 and extends at least a portion of the lengthof the cylindrical portion 217, FIG. 3 of the core 210. In anotherembodiment of the heat sink 200, a plurality of cooling ribbons 400 arepressed onto the heat sink 200 and extend at least a portion of thelength of the cylindrical portion 217 of the core 210. Heat in thesurface 212 of the core 210 transfers to the cooling ribbon 400 via thecontact portions 410. The heat is then convected into the surroundingatmosphere. An air blowing device, such as a fan or duct work, not shownin FIG. 12, may force air in the inner air channel 420 and the outer airchannel 422 to increase the convection of the heat in the inner airchannel 420 to the surrounding atmosphere.

Referring to FIG. 13, as with other embodiments of the heat sink 200, ashroud 430 may be placed over the heat sink 200. The shroud 430, inconjunction with an air blowing device, forces air in the outer airchannel 422 to remain in the outer air channel 422 throughout the lengthof the shroud 430. Accordingly, air in the outer air channel 422 is usedmore efficiently, which improves the overall efficiency of the coolingdevice 100.

Referring to FIG. 14, in another embodiment of the heat sink 200, thecooling fins 246 extend axially along the length of the core 210 similarto the ribbon-type cooling fin 400 of FIG. 12. More specifically, thecooling fins 246 may extend substantially parallel to the reference axisAA. This cooling fin configuration may be used when the air flow fromthe air blowing device 110 extends substantially parallel to thereference axis AA. For example, in the embodiment where the air blowingdevice 110 is duct work, the airflow generated by the air blowing device110 will likely extend along the reference axis AA as shown in FIG. 14.Thus, the benefits of having the cooling fins 246 parallel to the airflow as described above are maintained.

The cooling fins 246 shown in FIG. 14 and the cylindrical portion 217 ofthe core 210 may be extruded as a single piece. Accordingly, heattransfer between the core 210 and the cooling fins 246 is may beimproved. As with the other embodiments of the cooling device 100, ashroud, not shown in FIG. 14, may substantially encompass the core 210and the cooling fins 246.

The cores 210 of the heat sinks 200 described above may alternatively beconstructed from two pieces of material as shown in FIG. 15. Thecylindrical portion 217 may be manufactured separate from the taperedportion 218. The two portions may then be assembled so as to providethermal contact therebetween. In the embodiment shown in FIG. 15 a screw440 is used to attach the tapered portion 218 to the cylindrical portion217. It should be noted that other attaching mechanisms, such as the useof an adhesive may be used to attach the two portions together. Inanother embodiment, a heat conductive compound may be located betweenthe cylindrical portion and the tapered portion 218 in order to improvethe thermal conductivity between the two portions.

The embodiment of the core 210 shown in FIG. 15 facilitatesmanufacturing the core 210 and any cooling fins that may be attachedthereto by extrusion. With additional reference to FIGS. 12 and 14, anyof the embodiments of the heat sink 200 having cooling fins that extendalong the reference axis AA may be extruded from the same piece ofmaterial as the core 210. The extruded core and cooling fin combinationmay be cut to an appropriate size. The tapered portion 218 may then beadded to the combination to form the heat sink 200.

Referring again to FIG. 6, the fin rings 240 have been described asbeing adjacent to the surface 212 of the core 210. It is to beunderstood that the fin rings 240 may be attached to the core bynumerous methods. For example, the fin rings 240 may be pressed onto thecore 210. In another example, the core fin rings 240 may be soldered orbrazed to the core 210.

Another embodiment of a shroud 450 is shown in FIG. 15. As shown in FIG.15, the shroud 450 does not extend the full length of the fan 110. Thisembodiment of the shroud 450 may increase air flow by causing air toenter the cooling device 100 by way of an airflow 460 and an airflow462.

While an illustrative and presently preferred embodiment of theinvention has been described in detail herein, it is to be understoodthat the inventive concepts may be otherwise variously embodied andemployed and that the appended claims are intended to be construed toinclude such variations except insofar as limited by the prior art.

What is claimed is:
 1. A heat sink for removing heat from a heat source,said heat sink comprising: a core member comprising at least one coremember first surface, said at least one first surface being adapted tocontact at least a portion of said heat source; at least one outerperipheral surface located on said core member, at least a portion ofsaid at least one outer peripheral surface being tapered, wherein thecircumference of said at least one outer peripheral surface in theproximity of said first surface being greater than the circumference ofsaid at least one outer peripheral surface not in the proximity of saidfirst surface; at least one cooling fin operatively connected to said atleast one outer peripheral surface, said at least one cooling finextending in a direction substantially normal to said at least one coremember first surface; and a shroud having at least one inner surface,wherein said at least one inner surface is located adjacent said atleast one cooling fin, wherein said shroud has a first portion and asecond portion, wherein said first portion is located adjacent said atleast one cooling fin, wherein said second portion extends beyond saidcore member, and wherein said second portion has at least one slotformed therein.
 2. The heat sink of claim 1, wherein the circumferenceof said at least one outer peripheral surface is greatest at a junctionof said at least one outer peripheral surface and said at least onefirst surface.
 3. The heat sink of claim 1, wherein said at least aportion of said at least one outer peripheral surface being taperedforms a continuous surface.
 4. The heat sink of claim 1, wherein said atleast one cooling fin provides at least one air channel, and said atleast one air channel being adjacent said at least one cooling fin. 5.The heat sink of claim 4, and further comprising at least one secondcooling fin, wherein said at least one second cooling fin bisects saidat least one air channel.
 6. The heat sink of claim 1, and furthercomprising a cooling fin device comprising a collar member, wherein saidat least one cooling fin is attached to said collar member, said coolingfin device being in thermal contact with said at least one outerperipheral surface.
 7. The heat sink of claim 6, wherein an interferencefit exists between said at least one outer peripheral surface of saidcore member and said cooling fin device.
 8. The heat sink of claim 1,wherein said core member comprises a heat pipe.
 9. The heat sink ofclaim 1, wherein said core member further comprises a core member secondsurface oppositely disposed said at least one first surface, and whereinsaid heat sink further comprises an air blowing device located in thevicinity of said core member second surface.
 10. The heat sink of claim9, wherein said air blowing device has an air path associated therewith,and wherein said air path is extends in a direction between said atleast one core member first surface and said core member second surface.11. The heat sink of claim 1, wherein said at least one cooling fin hasa first end and a second end, wherein both said first end and saidsecond end are adjacent said at least one outer peripheral surface ofsaid core member.
 12. The heat sink of claim 1, wherein said core membercomprises a core first portion and a core second portion being inthermal contact, said core first portion comprising the portion of saidat least one outer peripheral surface being tapered.
 13. The heat sinkof claim 12, wherein said core second portion and said at least onecooling fin are formed from a single piece of material.
 14. The heatsink of claim 12, wherein said core second portion and said at least onecooling fin are extruded.
 15. A heat sink for removing heat from a heatsource, said heat sink comprising: a core member comprising at least onecore member first surface, said at least one first surface being adaptedto contact at least a portion of said heat source; at least one outerperipheral surface located on said core member; and at least one coolingfin operatively connected to said at least one outer peripheral surface,said at least one cooling fin extending in a direction substantiallynormal to said at least one core member first surface; at least aportion of said at least one outer peripheral surface being tapered,wherein the circumference of said at least one outer peripheral surfacein the proximity of said first surface being greater than thecircumference of said at least one outer peripheral surface not in theproximity of said first surface, wherein said at least a portion of saidcore member and said at least one cooling fin are extruded from a singlepiece of material.
 16. The heat sink of claim 15, wherein thecircumference of said at least one outer peripheral surface is greatestat a junction of said at least one outer peripheral surface and said atleast one first surface.
 17. The heat sink of claim 15, wherein said atleast a portion of said at least one outer peripheral surface beingtapered forms a continuous surface.
 18. The heat sink of claim 15,wherein said at least one cooling fin provides at least one air channel,and said at least one air channel being adjacent said at least onecooling fin.
 19. The heat sink of claim 18, and further comprising atleast one second cooling fin, wherein said at least one second coolingfin bisects said at least one air channel.
 20. The heat sink of claim15, and further comprising a cooling fin device comprising a collarmember, wherein said at least one cooling fin is attached to said collarmember, said cooling fin device being in thermal contact with said atleast one outer peripheral surface.
 21. The heat sink of claim 20,wherein an interference fit exists between said at least one outerperipheral surface of said core member and said cooling fin device. 22.The heat sink of claim 15, wherein said core member comprises a heatpipe.
 23. The heat sink of claim 15, wherein said core member furthercomprises a core member second surface oppositely disposed said at leastone first surface, and wherein said heat sink further comprises an airblowing device located in the vicinity of said core member secondsurface.
 24. The heat sink of claim 23, wherein said air blowing devicehas an air path associated therewith, and wherein said air path isextends in a direction between said at least one core member firstsurface and said core member second surface.
 25. The heat sink of claim15, wherein said at least one cooling fin has a first end and a secondend, wherein both said first end and said second end are adjacent saidat least one outer peripheral surface of said core member.
 26. The heatsink of claim 15, wherein said core member comprises a core firstportion and a core second portion being in thermal contact, said corefirst portion comprising the portion of said at least one outerperipheral surface being tapered.
 27. The heat sink of claim 26, whereinsaid core second portion and said at least one cooling fin are formedfrom a single piece of material.
 28. The heat sink of claim 26, whereinsaid core second portion and said at least one cooling fin are extruded.